The overall long-term goal of this project is the development of safer, more effective drugs for the treatment of prostate cancer (PC). Androgen receptor [AR, including its splice variants] and Mnk activated eIF4E signaling promote the development, progression, and metastasis of PC, in addition to induction of resistance to a variety of drugs. We recently developed clinical candidate galeterone (gal) which disrupts AR signaling via multiple mechanisms of action (1). Gal progressed into pivotal Phase III clinical trial in patients with metastatic castration- resistant PC (mCRPC) whose tumor cells express splice variant AR-V7 (ARMOR3-SV). However, the recent termination of this trial (due to trial design flaws) and the required 2550 mg/day high therapeutic dose of gal underscores the need to further systematic refinements to enable development of the next generation gal analogs (NGGAs) with enhanced efficacies and high therapeutic indices at low dose-administration expected to result in safer, more effective treatments across all stages/forms of PC. In the course of studies to develop NGGAs to modulate AR signaling in PC models (2), we discovered that gal and its new more efficacious analogs (VNPP414 and VNPP433-3?) also effectively target oncogenic eukaryotic protein translation, via modulation of Mnk-eIF4E axis (3). These compounds also suppress oncogenic peIF4E via degradation of Mnk1 and 2, and as such, are also referred to as Mnk degrading agents (MNKDAs). The objective of this application is to determine the therapeutic potential of lead NGGA, VNPP433-3? that simultaneously target both AR/AR-V7 and Mnk/eIF4E for the treatment of all forms of PC, including metastatic disease. In preliminary studies, gal and our new lead NGGAs degraded AR/AR-Vs, Mnk1/2, inhibited PSA synthesis and secretion, blocked cell cycle progression and growth of human PC cells in culture, induced apoptosis, and inhibited cell migration, invasion, and putative stem cell markers and reversed the expression of epithelial-to-mesenchymal transition (EMT), suggesting a direct inhibitory effect on the neoplastic process. In addition, the new NGGAs (alone and in combination) also inhibited the growth of gal-, enzalutamide-, docetaxel-, and mitoxantrone-resistant human PC cell lines. Importantly, initial in vivo testing showed that VNPP433-3? (at 7.53-fold lower equimolar dose than gal) markedly suppressed (84% vs. gal, 47%; p < 0.01) the growth of castration-resistant 22Rv1 xenograft tumors, with no apparent host toxicity. Based on these strong preliminary data, we hypothesize that our novel NGGAs possess superb multiple desirable anti-PC activities as single agents and can synergize (with increased anti-PC activity) when combined with FDA approved PC drugs. In this proposal, we will conduct, through 3 comprehensive and hypothesis-driven specific aims, basic/translational pre-clinical research, focusing on lead VNPP433-3?, with the goal to understand the full mechanisms of action against PC and its translational potential. Successful completion of the proposed studies will provide the toxicological, pharmacological and mechanistic data (including biomarker(s) identification) to support advanced preclinical IND-enabling studies and eventual clinical development.